It is common to utilize a spacer to take up space between two bearings on an automotive pinion, where the spacer is made from extruded tubular steel. It is not uncommon for such a tubular spacer to be collapsible (whereat a bulge is formed), so as to preload the bearings. However, conventional collapsible spacers are limited to a maximum stiffness load, at 0.75 mm deflection, of approximately 100 kilo-Newtons, which is due to the limitations of a bulge forming process that is utilized during installation of the collapsible tubular spacer.
In order to make a spacer bend more easily, some collapsible spacers have perforations placed through the tubular spacer wall. However, for these collapsible spacers, the perforations are placed away from a crush zone, which is typically at the center of the tubular spacer. Consequently, by placing the perforations away from the center of the conventional tubular spacer, the stiffness of these spacers are significantly decreased.
In addition, disposing perforations within tubular steel is expensive, which is due in part to the limited number of collapsible spacer manufacturers. Also, when the perforations are placed away from the center of the tubular spacer, it is required to re-engineer the crush zone at the center of the conventional tubular spacer in order to account for various parameters, like axial stiffness, bulge size control, and bulge location within the space between the two bearings on an automotive pinion shaft. Consequently, a steel tube that is perforated away from its center adds additional cost to the perforated tubular spacer. In addition to these negative cost effects that are associated with conventional perforated tubular spacers, it is difficult to adjust their spring rates.
As an example, U.S. Pat. No. 3,952,608 to Kanai discloses a collapsible spacer in a final drive unit of a motor vehicle having openings 20 as illustrated in FIGS. 1 and 2 of the Kanai patent. As shown, the openings 20 of the Kanai patent are in an area of the collapsible spacer that is away from the crush zone.
Since conventional collapsible spacers are made directly from extruded tubing the spring rate is not easily adjusted and therefore, the cost of the tubing further increases as its size increases. Also, it might be necessary for conventional spacers to have their material properties adjusted without perforating the wall of such a spacer so as to achieve deformation in a different manner. Unfortunately, recent design aspects in axles, such as plug-on propshafts, are requiring larger diameter pinion nuts that provide higher nut torque to resist loosening, so as to a achieve a much higher clamping force on more robust spacers. Consequently, there is a need for next generation collapsible spacers to resist these much higher clamp loads.
Therefore, what is sought is a collapsible spacer having perforations in a central portion thereof that is not constructed from extruded tubular steel. Such a perforated collapsible spacer must not lower axial stiffness at its center nor negatively affect the crush zone, bulge size, and bulge location. Such a perforated collapsible spacer must be able to cooperate with new axles that require higher nut torque to resist loosening, which in turn require higher clamp forces, so as to resist higher clamp loads. In addition, this perforated collapsible spacer needs to be less expensive to manufacture than a conventional tubular perforated collapsible spacer.